Australia's Nick Kyrgios beat Tomas Berdych for the second time in six days to progress to the semi-finals of the Dubai Tennis Championships.
Kyrgios, 20, received treatment on-court and overcame back pain to beat the world number seven 6-4 6-4.
Last week Kyrgios beat Berdych, again in straight sets, en route to his first career title in Marseille.
World number one Novak Djokovic faces sixth-seed Feliciano Lopez in the last quarter-final later on Thursday.
"I was in pain at the start, I've played a lot of matches in a row now," Kyrgios said after his eighth successive victory.
"Tomas is a tough player, one of the best in the world. I served well and competed well. I'm very, very happy."
The Australian will next face Swiss second seed Stan Wawrinka, who beat Germany's Philipp Kohlschreiber 7-5 6-1.
Britain's Jamie Murray and Tommy Robredo of Spain were beaten 6-4 6-3 by Italians Simone Bolelli and Andreas Seppi in the doubles.